Sorry guys, it has to be said: Erebor is lacking, leaving us wanting.
Not even attempting to relate to the lore, we do have in game experience from two dwarf fortresses/dungeons.
Thorins Hall and Moria.
Obviously not counting Zigilgund, Othrikar or other places as even comparable by a longshot in this.
So that leaves Erebor, still under construction we hope. Basically it is a larger Thorins Hall, with even less dungeons and minor halls. The entirety of Erebor would probably fit INSIDE the 21's Hall of Moria.
So what does it leave us? I think we expect something in between Moria and Thorins Hall, maybe half the size on the habitable areas of Moria, not counting Foundations of Stone or Redhorn Lodes here, but The Delvings, Dolven-View, 21st Hall, 1st Hall and some more. That might have been a decent size for Erebor, plus some dungeons. Since Erebor is in fact inhabited and has been worked on by dwarves for ages, it should of course look more finished and polished. Zelem Melek comes to mind. Black and gold stone, very impressive.
You have a good start, but right now its just a larger Thorins Hall.